add alloc/no_std support

Cargo.toml

@@ -16,7 +16,7 @@ travis-ci = { repository = "serde-rs/json" }
 appveyor = { repository = "serde-rs/json" }
 
 [dependencies]
-serde = "1.0.60"
+serde = { version = "1.0.60", default-features = false }
 indexmap = { version = "1.2", optional = true }
 itoa = "0.4.3"
 ryu = "1.0"
@@ -42,7 +42,11 @@ features = ["raw_value"]
 ### FEATURES #################################################################
 
 [features]
-default = []
+default = ["std"]
+
+std = ["serde/std"]
+
+alloc = ["serde/alloc"]
 
 # Use a different representation for the map type of serde_json::Value.
 # This allows data to be read into a Value and written back to a JSON string

src/de.rs

@@ -1,10 +1,14 @@
 //! Deserialize JSON data to a Rust data structure.
 
-use std::io;
+use io;
-use std::marker::PhantomData;
+use core::marker::PhantomData;
-use std::result;
+use core::result;
-use std::str::FromStr;
+use core::str::FromStr;
-use std::{i32, u64};
+use core::{i32, u64};
+#[cfg(feature = "alloc")]
+use alloc::string::String;
+#[cfg(feature = "alloc")]
+use alloc::vec::Vec;
 
 use serde::de::{self, Expected, Unexpected};
 

src/error.rs

@@ -1,10 +1,15 @@
 //! When serializing or deserializing JSON goes wrong.
 
+#[cfg(feature = "std")]
 use std::error;
-use std::fmt::{self, Debug, Display};
+use core::fmt::{self, Debug, Display};
-use std::io;
+use io;
-use std::result;
+use core::result;
-use std::str::FromStr;
+use core::str::FromStr;
+#[cfg(feature = "alloc")]
+use alloc::boxed::Box;
+#[cfg(feature = "alloc")]
+use alloc::string::{String, ToString};
 
 use serde::de;
 use serde::ser;
@@ -131,6 +136,7 @@ pub enum Category {
 }
 
 #[cfg_attr(feature = "cargo-clippy", allow(fallible_impl_from))]
+#[cfg(feature = "std")]
 impl From<Error> for io::Error {
     /// Convert a `serde_json::Error` into an `io::Error`.
     ///
@@ -333,6 +339,7 @@ impl Display for ErrorCode {
     }
 }
 
+#[cfg(feature = "std")]
 impl error::Error for Error {
     fn source(&self) -> Option<&(error::Error + 'static)> {
         match self.err.code {
@@ -342,6 +349,9 @@ impl error::Error for Error {
     }
 }
 
+#[cfg(not(feature = "std"))]
+impl serde::de::StdError for Error {}
+
 impl Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         Display::fmt(&*self.err, f)

src/io.rs

@@ -0,0 +1,79 @@
+#[cfg(not(feature = "std"))]
+use core::slice;
+
+#[cfg(feature = "std")]
+pub use std::io::{Result, Write, Read, Error, Bytes, ErrorKind};
+
+#[cfg(not(feature = "std"))]
+pub type Error = &'static str;
+
+#[cfg(not(feature = "std"))]
+pub type Result<T> = core::result::Result<T, Error>;
+
+#[cfg(not(feature = "std"))]
+pub trait Write {
+    fn write(&mut self, buf: &[u8]) -> Result<usize>;
+
+    fn write_all(&mut self, mut buf: &[u8]) -> Result<()> {
+        while !buf.is_empty() {
+            match self.write(buf) {
+                Ok(0) => return Err("failed to write whole buffer"),
+                Ok(n) => buf = &buf[n..],
+                Err(e) => return Err(e),
+            }
+        }
+        Ok(())
+    }
+
+    fn flush(&mut self) -> Result<()>;
+}
+
+#[cfg(not(feature = "std"))]
+impl<W: Write> Write for &mut W {
+    fn write(&mut self, buf: &[u8]) -> Result<usize> {
+        (*self).write(buf)
+    }
+
+    fn flush(&mut self) -> Result<()> {
+        (*self).flush()
+    }
+}
+
+#[cfg(all(not(feature = "std"), feature = "alloc"))]
+impl Write for &mut serde::export::Vec<u8> {
+    fn write(&mut self, buf: &[u8]) -> Result<usize> {
+        self.extend(buf);
+        Ok(buf.len())
+    }
+
+    fn flush(&mut self) -> Result<()> {Ok(())}
+}
+
+#[cfg(not(feature = "std"))]
+pub trait Read {
+    fn read(&mut self, buf: &mut [u8]) -> Result<usize>;
+    fn bytes(self) -> Bytes<Self> where Self: Sized {
+        Bytes {
+            inner: self,
+        }
+    }
+}
+
+#[cfg(not(feature = "std"))]
+pub struct Bytes<R> {
+    inner: R,
+}
+
+#[cfg(not(feature = "std"))]
+impl<R: Read> Iterator for Bytes<R> {
+    type Item = Result<u8>;
+
+    fn next(&mut self) -> Option<Result<u8>> {
+        let mut byte = 0;
+        match self.inner.read(slice::from_mut(&mut byte)) {
+            Ok(0) => None,
+            Ok(..) => Some(Ok(byte)),
+            Err(e) => Some(Err(e)),
+        }
+    }
+}

src/iter.rs

@@ -1,4 +1,4 @@
-use std::io;
+use io;
 
 pub struct LineColIterator<I> {
     iter: I,

src/lib.rs

@@ -331,6 +331,7 @@
     must_use_candidate,
 ))]
 #![deny(missing_docs)]
+#![cfg_attr(not(feature = "std"), no_std)]
 
 #[macro_use]
 extern crate serde;
@@ -338,6 +339,10 @@ extern crate serde;
 extern crate indexmap;
 extern crate itoa;
 extern crate ryu;
+#[cfg(feature = "std")]
+extern crate core;
+#[cfg(feature = "alloc")]
+extern crate alloc;
 
 #[doc(inline)]
 pub use self::de::{from_reader, from_slice, from_str, Deserializer, StreamDeserializer};
@@ -355,8 +360,8 @@ pub use self::value::{from_value, to_value, Map, Number, Value};
 macro_rules! try {
     ($e:expr) => {
         match $e {
-            ::std::result::Result::Ok(val) => val,
+            ::core::result::Result::Ok(val) => val,
-            ::std::result::Result::Err(err) => return ::std::result::Result::Err(err),
+            ::core::result::Result::Err(err) => return ::core::result::Result::Err(err),
         }
     };
 }
@@ -370,6 +375,7 @@ pub mod map;
 pub mod ser;
 pub mod value;
 
+mod io;
 mod iter;
 mod number;
 mod read;

src/map.rs

@@ -7,15 +7,19 @@
 //! [`IndexMap`]: https://docs.rs/indexmap/*/indexmap/map/struct.IndexMap.html
 
 use serde::{de, ser};
-use std::borrow::Borrow;
+use core::borrow::Borrow;
-use std::fmt::{self, Debug};
+use core::fmt::{self, Debug};
-use std::hash::Hash;
+use core::hash::Hash;
-use std::iter::FromIterator;
+use core::iter::FromIterator;
-use std::ops;
+use core::ops;
 use value::Value;
+#[cfg(feature = "alloc")]
+use alloc::string::String;
 
-#[cfg(not(feature = "preserve_order"))]
+#[cfg(all(not(feature = "preserve_order"), feature = "std"))]
 use std::collections::{btree_map, BTreeMap};
+#[cfg(all(not(feature = "preserve_order"), feature = "alloc"))]
+use alloc::collections::{btree_map, BTreeMap};
 
 #[cfg(feature = "preserve_order")]
 use indexmap::{self, IndexMap};
@@ -151,8 +155,10 @@ impl Map<String, Value> {
     {
         #[cfg(feature = "preserve_order")]
         use indexmap::map::Entry as EntryImpl;
-        #[cfg(not(feature = "preserve_order"))]
+        #[cfg(all(not(feature = "preserve_order"), feature = "std"))]
         use std::collections::btree_map::Entry as EntryImpl;
+        #[cfg(all(not(feature = "preserve_order"), feature = "alloc"))]
+        use alloc::collections::btree_map::Entry as EntryImpl;
 
         match self.map.entry(key.into()) {
             EntryImpl::Vacant(vacant) => Entry::Vacant(VacantEntry { vacant: vacant }),

src/number.rs

@@ -1,7 +1,7 @@
 use error::Error;
 use serde::de::{self, Unexpected, Visitor};
 use serde::{Deserialize, Deserializer, Serialize, Serializer};
-use std::fmt::{self, Debug, Display};
+use core::fmt::{self, Debug, Display};
 
 #[cfg(feature = "arbitrary_precision")]
 use itoa;

src/read.rs

@@ -1,5 +1,8 @@
-use std::ops::Deref;
+use core::ops::Deref;
-use std::{char, cmp, io, str};
+use io;
+use core::{char, cmp, str};
+#[cfg(feature = "alloc")]
+use alloc::vec::Vec;
 
 #[cfg(feature = "raw_value")]
 use serde::de::Visitor;

src/ser.rs

@@ -1,9 +1,13 @@
 //! Serialize a Rust data structure into JSON data.
 
-use std::fmt;
+use core::fmt;
-use std::io;
+use io;
-use std::num::FpCategory;
+use core::num::FpCategory;
-use std::str;
+use core::str;
+#[cfg(feature = "alloc")]
+use alloc::string::{String, ToString};
+#[cfg(feature = "alloc")]
+use alloc::vec::Vec;
 
 use super::error::{Error, ErrorCode, Result};
 use serde::ser::{self, Impossible, Serialize};
@@ -460,7 +464,7 @@ where
     where
         T: fmt::Display,
     {
-        use std::fmt::Write;
+        use core::fmt::Write;
 
         struct Adapter<'ser, W: 'ser, F: 'ser> {
             writer: &'ser mut W,
@@ -1634,6 +1638,7 @@ pub trait Formatter {
 
     /// Writes an integer value like `-123` to the specified writer.
     #[inline]
+    #[cfg(feature = "std")]
     fn write_i8<W: ?Sized>(&mut self, writer: &mut W, value: i8) -> io::Result<()>
     where
         W: io::Write,
@@ -1643,6 +1648,19 @@ pub trait Formatter {
 
     /// Writes an integer value like `-123` to the specified writer.
     #[inline]
+    #[cfg(not(feature = "std"))]
+    fn write_i8<W: ?Sized>(&mut self, writer: &mut W, value: i8) -> io::Result<()>
+    where
+        W: io::Write,
+    {
+        let mut buffer = itoa::Buffer::new();
+        let s = buffer.format(value);
+        writer.write_all(s.as_bytes())
+    }
+
+    /// Writes an integer value like `-123` to the specified writer.
+    #[inline]
+    #[cfg(feature = "std")]
     fn write_i16<W: ?Sized>(&mut self, writer: &mut W, value: i16) -> io::Result<()>
     where
         W: io::Write,
@@ -1652,6 +1670,19 @@ pub trait Formatter {
 
     /// Writes an integer value like `-123` to the specified writer.
     #[inline]
+    #[cfg(not(feature = "std"))]
+    fn write_i16<W: ?Sized>(&mut self, writer: &mut W, value: i16) -> io::Result<()>
+    where
+        W: io::Write,
+    {
+        let mut buffer = itoa::Buffer::new();
+        let s = buffer.format(value);
+        writer.write_all(s.as_bytes())
+    }
+
+    /// Writes an integer value like `-123` to the specified writer.
+    #[inline]
+    #[cfg(feature = "std")]
     fn write_i32<W: ?Sized>(&mut self, writer: &mut W, value: i32) -> io::Result<()>
     where
         W: io::Write,
@@ -1661,6 +1692,19 @@ pub trait Formatter {
 
     /// Writes an integer value like `-123` to the specified writer.
     #[inline]
+    #[cfg(not(feature = "std"))]
+    fn write_i32<W: ?Sized>(&mut self, writer: &mut W, value: i32) -> io::Result<()>
+    where
+        W: io::Write,
+    {
+        let mut buffer = itoa::Buffer::new();
+        let s = buffer.format(value);
+        writer.write_all(s.as_bytes())
+    }
+
+    /// Writes an integer value like `-123` to the specified writer.
+    #[inline]
+    #[cfg(feature = "std")]
     fn write_i64<W: ?Sized>(&mut self, writer: &mut W, value: i64) -> io::Result<()>
     where
         W: io::Write,
@@ -1668,8 +1712,21 @@ pub trait Formatter {
         itoa::write(writer, value).map(drop)
     }
 
+    /// Writes an integer value like `-123` to the specified writer.
+    #[inline]
+    #[cfg(not(feature = "std"))]
+    fn write_i64<W: ?Sized>(&mut self, writer: &mut W, value: i64) -> io::Result<()>
+    where
+        W: io::Write,
+    {
+        let mut buffer = itoa::Buffer::new();
+        let s = buffer.format(value);
+        writer.write_all(s.as_bytes())
+    }
+
     /// Writes an integer value like `123` to the specified writer.
     #[inline]
+    #[cfg(feature = "std")]
     fn write_u8<W: ?Sized>(&mut self, writer: &mut W, value: u8) -> io::Result<()>
     where
         W: io::Write,
@@ -1679,6 +1736,19 @@ pub trait Formatter {
 
     /// Writes an integer value like `123` to the specified writer.
     #[inline]
+    #[cfg(not(feature = "std"))]
+    fn write_u8<W: ?Sized>(&mut self, writer: &mut W, value: u8) -> io::Result<()>
+    where
+        W: io::Write,
+    {
+        let mut buffer = itoa::Buffer::new();
+        let s = buffer.format(value);
+        writer.write_all(s.as_bytes())
+    }
+
+    /// Writes an integer value like `123` to the specified writer.
+    #[inline]
+    #[cfg(feature = "std")]
     fn write_u16<W: ?Sized>(&mut self, writer: &mut W, value: u16) -> io::Result<()>
     where
         W: io::Write,
@@ -1688,6 +1758,19 @@ pub trait Formatter {
 
     /// Writes an integer value like `123` to the specified writer.
     #[inline]
+    #[cfg(not(feature = "std"))]
+    fn write_u16<W: ?Sized>(&mut self, writer: &mut W, value: u16) -> io::Result<()>
+    where
+        W: io::Write,
+    {
+        let mut buffer = itoa::Buffer::new();
+        let s = buffer.format(value);
+        writer.write_all(s.as_bytes())
+    }
+
+    /// Writes an integer value like `123` to the specified writer.
+    #[inline]
+    #[cfg(feature = "std")]
     fn write_u32<W: ?Sized>(&mut self, writer: &mut W, value: u32) -> io::Result<()>
     where
         W: io::Write,
@@ -1697,6 +1780,19 @@ pub trait Formatter {
 
     /// Writes an integer value like `123` to the specified writer.
     #[inline]
+    #[cfg(not(feature = "std"))]
+    fn write_u32<W: ?Sized>(&mut self, writer: &mut W, value: u32) -> io::Result<()>
+    where
+        W: io::Write,
+    {
+        let mut buffer = itoa::Buffer::new();
+        let s = buffer.format(value);
+        writer.write_all(s.as_bytes())
+    }
+
+    /// Writes an integer value like `123` to the specified writer.
+    #[inline]
+    #[cfg(feature = "std")]
     fn write_u64<W: ?Sized>(&mut self, writer: &mut W, value: u64) -> io::Result<()>
     where
         W: io::Write,
@@ -1704,6 +1800,18 @@ pub trait Formatter {
         itoa::write(writer, value).map(drop)
     }
 
+    /// Writes an integer value like `123` to the specified writer.
+    #[inline]
+    #[cfg(not(feature = "std"))]
+    fn write_u64<W: ?Sized>(&mut self, writer: &mut W, value: u64) -> io::Result<()>
+    where
+        W: io::Write,
+    {
+        let mut buffer = itoa::Buffer::new();
+        let s = buffer.format(value);
+        writer.write_all(s.as_bytes())
+    }
+
     /// Writes a floating point value like `-31.26e+12` to the specified writer.
     #[inline]
     fn write_f32<W: ?Sized>(&mut self, writer: &mut W, value: f32) -> io::Result<()>

src/value/de.rs

@@ -1,8 +1,18 @@
+#[cfg(feature = "std")]
 use std::borrow::Cow;
-use std::fmt;
+#[cfg(feature = "alloc")]
-use std::slice;
+use alloc::borrow::{Cow, ToOwned};
-use std::str;
+use core::fmt;
+use core::slice;
+use core::str;
+#[cfg(feature = "std")]
 use std::vec;
+#[cfg(feature = "alloc")]
+use alloc::vec;
+#[cfg(feature = "alloc")]
+use alloc::string::String;
+#[cfg(feature = "alloc")]
+use alloc::vec::Vec;
 
 use serde;
 use serde::de::{

src/value/from.rs

@@ -1,4 +1,11 @@
+#[cfg(feature = "std")]
 use std::borrow::Cow;
+#[cfg(feature = "alloc")]
+use alloc::borrow::Cow;
+#[cfg(feature = "alloc")]
+use alloc::string::{String, ToString};
+#[cfg(feature = "alloc")]
+use alloc::vec::Vec;
 
 use super::Value;
 use map::Map;
@@ -182,7 +189,7 @@ impl<'a, T: Clone + Into<Value>> From<&'a [T]> for Value {
     }
 }
 
-impl<T: Into<Value>> ::std::iter::FromIterator<T> for Value {
+impl<T: Into<Value>> ::core::iter::FromIterator<T> for Value {
     /// Convert an iteratable type to a `Value`
     ///
     /// # Examples

src/value/index.rs

@@ -1,5 +1,9 @@
-use std::fmt;
+use core::fmt;
-use std::ops;
+use core::ops;
+#[cfg(feature = "alloc")]
+use alloc::string::String;
+#[cfg(feature = "alloc")]
+use alloc::borrow::ToOwned;
 
 use super::Value;
 use map::Map;
@@ -132,6 +136,9 @@ where
 
 // Prevent users from implementing the Index trait.
 mod private {
+    #[cfg(feature = "alloc")]
+    use alloc::string::String;
+
     pub trait Sealed {}
     impl Sealed for usize {}
     impl Sealed for str {}

src/value/mod.rs

@@ -90,10 +90,14 @@
 //! [from_slice]: https://docs.serde.rs/serde_json/de/fn.from_slice.html
 //! [from_reader]: https://docs.serde.rs/serde_json/de/fn.from_reader.html
 
-use std::fmt::{self, Debug};
+use core::fmt::{self, Debug};
-use std::io;
+use io;
-use std::mem;
+use core::mem;
-use std::str;
+use core::str;
+#[cfg(feature = "alloc")]
+use alloc::string::String;
+#[cfg(feature = "alloc")]
+use alloc::vec::Vec;
 
 use serde::de::DeserializeOwned;
 use serde::ser::Serialize;
@@ -194,11 +198,16 @@ struct WriterFormatter<'a, 'b: 'a> {
 
 impl<'a, 'b> io::Write for WriterFormatter<'a, 'b> {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        #[cfg(feature = "std")]
         fn io_error<E>(_: E) -> io::Error {
             // Error value does not matter because fmt::Display impl below just
             // maps it to fmt::Error
             io::Error::new(io::ErrorKind::Other, "fmt error")
         }
+        #[cfg(not(feature = "std"))]
+        fn io_error<E>(_: E) -> &'static str {
+            "fmt error"
+        }
         let s = try!(str::from_utf8(buf).map_err(io_error));
         try!(self.inner.write_str(s).map_err(io_error));
         Ok(buf.len())

src/value/partial_eq.rs

@@ -1,4 +1,6 @@
 use super::Value;
+#[cfg(feature = "alloc")]
+use alloc::string::String;
 
 fn eq_i64(value: &Value, other: i64) -> bool {
     value.as_i64().map_or(false, |i| i == other)

src/value/ser.rs

@@ -6,6 +6,13 @@ use map::Map;
 use number::Number;
 use value::{to_value, Value};
 
+#[cfg(feature = "alloc")]
+use alloc::string::{String, ToString};
+#[cfg(feature = "alloc")]
+use alloc::vec::Vec;
+#[cfg(feature = "alloc")]
+use alloc::borrow::ToOwned;
+
 impl Serialize for Value {
     #[inline]
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>